It involves making a volcano that, based on a reaction between baking soda and vinegar, spews out a bubbly flow of "lava".

The kids LOVE it! However, don't expect the volcano to blow its top off...

When I initially ran into this volcano project I couldn't help but imagine some sort of big explosion once the vinegar hit the baking soda (something like the picture below of myself sitting beside a REAL erupting volcano - the photo was taken in Zaire, Africa in 1991):

But, for a three, four or even five year old, a homemade volcano is as exciting as a real one is to a grownup. Even more because they get to actually create the chemical reaction themselves (and even stick their finger inside the caldera...)

If you have any doubts, the clip at the end of the photographed stages below shows my little girl, Maya's, excitement every time more vinegar or baking soda is added to the volcano.

There are a few basic items you'll need to create the volcano, then you can play around and experiment on your own. Here are the basic items:

A cylindrical container like a plastic bottle.

Baking soda

Warm water

Dishwashing liquid

Vinegar

Red and/or Yellow food coloring

Basically, you build a volcano around the bottle. Then pour about a cup of warm water into the bottle, add a tablespoon of dishwashing liquid, around 1/4 cup baking soda and a few drops of food coloring. To create the reaction, you pour vinegar inside the bottle and the fluid spews out.

You can make your volcano out of paper mache, playdough, even dirt or sand like we did below. It's up to you.

I've run into quite a few volcano fluid recipes. Some say to use water, others do it without. I didn't really follow any of them exactly, you pretty much need to experiment BEFORE you carry out an activity like this at a party.

During the party, make sure you have extra baking soda and vinegar because the kids usually want to do it again and again.

Here's our version of a backyard volcano made in less than 15 minutes and enjoyed for about an hour!

Make Volcano 1: We've set everything up and you can see the plastic bottle next to Maya's leg just before it is covered by dirt.

Make Volcano 2: Maya starts to cover the plastic bottle with the dirt.

Volcano 3: By patting down the dirt, the shape of the volcano has formed.

Volcano 4: For a true Jurassic feel, Maya added a few plastic dinos...

Make Volcano 5: ...and little trees and shrubs. Notice the top of the bottle.

Make Volcano 6: Here, Maya adds a "few" drops of food coloring to the bottle inside the volcano.

The Amazing Diet Coke and Mentos Volcano

I found a really cool volcano recipe online that really made an amazing effect! You'll need Diet Coke and Mentos to make the reaction!
After you make your volcano and everything, pour diet coke into the hidden bottle and then when you want the explosion to happen add one or a few mentos (at once... not one-by-one). You should do this outdoors!!
And here's the youtube video I saw that really helped me: